Biomedical porous NiTi shape memory alloy (SMA) is a promising implant material. The pore characteristics, such as pore morphology and distribution, mean pore size and porosity of porous NiTi SMA fabricated by combustion synthesis were investigated in this paper by optical microscopy, scanning electron microscopy (SEM), image processing and density determination and the mechanism of pore formation was proposed. The result indicated that pore morphology and distribution of porous NiTi SMA exhibited features of isotropy or anisotropy, depending upon preheating temperature during synthesis. Mean pore size and porosity range was 300-600 μm and 60-64% respectively, and open porosity ratio was bigger than 90% which indicates that porous NiTi SMA is suitable for biomedical application.